Bump isort from 5.8.0 to 5.9.1

Bumps [isort](https://github.com/pycqa/isort) from 5.8.0 to 5.9.1.
- [Release notes](https://github.com/pycqa/isort/releases)
- [Changelog](https://github.com/PyCQA/isort/blob/main/CHANGELOG.md)
- [Commits](PyCQA/isort@5.8.0...5.9.1)

---
updated-dependencies:
- dependency-name: isort
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

pyproject.toml

@@ -36,7 +36,7 @@ blacken-docs = "^1.10.0"
 coverage = {version = "^5.5", extras = ["toml"]}
 flake8 = "^3.9.1"
 flake8-docstrings = "^1.6.0"
-isort = "^5.8.0"
+isort = "^5.9.1"
 mypy = "^0.902"
 pre-commit = "^2.13.0"
 pre-commit-hooks = "^4.0.1"